static BWImage bwFoldImage_withCorners(BWImage big, BWImage pat) {
  int wp = pat.getWidth(), hp = pat.getHeight();
  int w = big.getWidth(), h = big.getHeight();
  BWImage out = new(w+wp, h+hp);
  for (int y = 0; y < h+hp; y++)
    for (int x = 0; x < w+wp; x++)
      out.setPixel(x, y, bwImageSectionsSimilarity2_partial(big, pat,
        x, y,
        max(0, wp-x), max(0, hp-y),
        min(wp, w+wp-x), min(hp, h+hp-y),
        0));
  ret out;
}

Began life as a copy of #1027289